EP1475161A2 - Process and device to supply metered material to a coating apparatus - Google Patents

Abstract

The method involves feeding coating and/or flushing material into a cylinder (12A,B) of a dosing unit (10A,B) and feeding it into the coating arrangement (1), especially via a line (27A,B) with a scraper. A piston is moved in the cylinder by a drive controlled to fill or empty the cylinder with a defined quantity of coating and/or flushing material. The pressure of the material in, fed to or removed from the cylinder is measured by a sensor (DSA,DSB) and coating system parameters are monitored using the resulting measurement signal. Independent claims are also included for the following: (a) a supply system for dosed material supply for a coating arrangement (b) and a dosing unit for an inventive system.

Description

The invention relates to a method and a supply system for the metered material supply of a coating device in a plant for automatically controlled serial coating of workpieces according to the preamble of the independent claims. In particular, it is the electrostatic Series coating of workpieces such as Vehicle bodies with electrically conductive coating material often changing color.

For example, DE 101 57 966 describes a supply system of the type considered here, in which, in the known A / B technique, two mixed color lines lead from one color changer to one piston dispenser each, which serves as a coating device via another common line Atomizers are connected. As explained in DE 101 57 966, a piston dispenser is to be understood as meaning a metering unit in the cylinder of which the piston is moved by a metering drive which is controlled as required during the coating in such a way that it displaces the coating material in the demand-metered and variable quantity into the the nebulizer leading line expresses because it is usually necessary during the coating, to change the amount of color or coating material to be supplied to the nebulizer, for example, depending on workpiece areas, size and shape of the surfaces to be coated, spray jet shape, etc. This volumetric metering, ie demand-dependent control of the volume flow with the piston feeder driven, for example, by a servomotor, also has significant advantages over other metering systems. For example, although the metering pumps which are also used volumetrically in many coating systems have a high metering accuracy, they are poorly flushable. By contrast, the color pressure regulators used for dosing in other systems (eg US Pat. No. 5,221,047) no longer meet today's demands on dosing accuracy. In contrast, piston dispensers are both very accurate and easily rinsed in a color change. They allow a precise metering not only of the coating material when applied by the atomizer and the filling of the piston dispenser, but also a flushing liquid to be filled with a desired volume in a line or the piston dispenser (EP 1362641). Piston dispensers can be designed to be extremely rigid (DE 102 33 633) and also enable, when used as intermediate container, the advantageous potential separation known from EP 0 292 778 between the high-voltage coating device and the grounded ink supply unit such as a color changer by emptying the lines in sections In modern coating systems is known to be realized by pigging technology (DE 199 37 426).
In coupled systems, piston dispensers moreover have the advantage that no gear metering pump must be present at the atomizer and therefore pig stations can be arranged inside the atomizer, whereby color and detergent losses can be reduced to a minimum (EP 1314480).

Problems exist in the coating systems of the considered here Genus but in that for monitoring and Controlling the system requires considerable effort, the often neither the desired optimization of the metering operation yet Ensures the required reliability. Some of these Problems are caused by the nature of the newts and the elastic tubes required for them, e.g. in Automotive coating equipment inside diameter between 5 and have 10 mm and can be more than 15 m long. At the zu Promotional liquids may be either colored or other coating material as well as the one needed for rinsing Thinner act.

From DE 100 65 608 is a system for scratch-resistant coating of vehicle bodies with an aqueous emulsion known, which initially pumped into an intermediate container and then conveyed from there through a line to a sprayer becomes. The intermediate container consists of a cylinder with a piston for emptying the intermediate container of a motor is driven. The emulsion should be the sprayer be supplied with regulated pressure. To this end is measured with a pressure sensor, the emulsion feed pressure and the sensor signal fed to a control device, which in turn controls the piston drive motor. With this pressure control is not a volumetric dosage of the coating material possible in the manner explained above.

From DE 101 20 077 a color coating system is known, in which arranged above a directly in front of the atomizer Pressure sensor detects the color pressure and then regulated can be. Furthermore, a pressure sensor may be on the supply line a provided outside of the ink path dosing for a sliding medium for the coating material, the ensure an adequate supply of push media should. A dosing unit into which the to be applied Coating material and / or a detergent is passed, is not scheduled.

The object of the invention is to specify a method or metering system the known from DE 101 57 966 genus, with in a simple way reliable monitoring and / or Control especially of several factors of the system allows becomes.

This object is solved by the features of the claims.

The invention is based on the finding that with a and same simple pressure sensor numerous different parameters or functions of the system both inside and outside monitored by the coating company, diagnosed and / or can be controlled. The size of the dosing cylinder or measured in the lines connected to it Fluid pressure can be e.g. for the optimization of the speed filling the dosing cylinder and connected Use cables and thus to avoid loss of time. In addition, this pressure allows conclusions to be made on such different factors such as pressure and / or pressure fluctuations the fluids in the supply system from which the dosing unit is filled (ring line pressure), viscosity of the subsidized Liquids and even wear of the pigs. Furthermore, the signal generated by the pressure sensor for Compensation of compliances of the molded hoses and other system components as well as changes in hose lengths and other system components and according to another Possibility to report pigging positions to be used.

In a typical embodiment of the invention is with the pressure sensor first when filling the cylinder of the dosing unit the pressure prevailing in or on the cylinder or if necessary negative pressure of the coating material (or rinsing material) monitored, in particular to avoid the intake of air. The filling is preferably volumetric due to Piston movement, i. with a predetermined volume and / or volume flow, the pressure monitoring system being controlled by controlling the Piston drive corrective intervention, if its speed is too high or will. Furthermore, the fluid pressure in the above-mentioned supply system (loop pressure) be measured. In the subsequent application process Serves with the required exact volumetric dosage the pressure monitoring then mainly for the protection of the dosing unit Downstream cables and components against impermissible high pressures and damage caused thereby.

On the embodiment shown in the drawing is the invention explained in more detail. It is a gemolchtes A / B system for the metered supply of an electrostatic Rotary atomizer with electrically conductive coating material often changing color.

The coating material is supplied to the atomizer 1 by a paint supply unit 2 such as supplied to an A / B color changer, the of two color change valve arrangements per se conventional type may consist of one operated according to the known A / B principle Double color change unit are composed. The Color valves FA and FB of unit 2 can be connected to the usual (not shown) ring lines of the paint supply system be connected.

At the two outputs of the unit 2 are each a pig station 6A and 6B, respectively, are broken hose lines 7A and 7B Insulating material connected, each with a further pig station 8A and 8B respectively in the cylinders 12A and 12B of a Piston doser 10A or 10B lead. The piston of this doser limits the color space formed in the cylinder and is of a (not shown) metering drive, such as a driven by a servo motor spindle drive, in the cylinder displaceable. Preferably, the mechanical components of the piston dispenser at least partially made of electrical insulating material with high modulus of elasticity as by name Ceramics consist, as in the already mentioned DE 102 33 633 described, after which the tensile and / or bending modulus of the material should be greater than 10 GPa.

From the cylinders 12A and 12B, respectively, the piston dispensers 10A and 10B leads via a respective pig station 28A and 28B one each further gemülchte hose 27A and 27B to one each Pig station 29A or 29B inside the atomizer 1. The piston feeder 10A and its pig stations 8A and 28A are appropriate assembled into a compact unit. The same thing applies to the piston dispenser 10B.

Depending on the mode of operation, the pigging stations for the recording be formed by one or more pigs.

For the controlled connections between the unit 2, the Pig stations, the piston dispensers and the hose lines expedient valve arrangements are provided in a conventional manner (not shown).

In the example considered, the piston dispensers 10A and 10B can be used 10B on the outside of the indicated at 3 wall of the spray booth arranged and with the atomizer 1 on violated lines 27A, 27B connected by the arm and at 4 indicated hand axis of a painting robot or another Painting machine are passed. In other cases Instead, the piston dispensers 10A and 10B may be in or on one of the machine arms be mounted as in the in Fig. 2 of already mentioned DE 101 57 966 system, of which the structure of the A / B system described here in addition to the Essentially differentiates the position of the piston dispenser only that the two piston dispensers 10A and 10B with the Atomizer 1 via the two gemold lines 27A, 27B instead of being connected via a common line. In further According to FIG. 2 of DE 101 57 966, one with potential separation operated separate rinsing circuit (not here shown), which is a further piston dispenser for example, the type described above and another gemold Line contains, on serving as a rinse thinner outside the lines 27A and 27B in the Atomizer 1 is passed.

In operation, of the unit 2, for example, first the Cylinder 12A by ring line pressure with one by automatic controlled backward movement of his piston accurately adjusted Volume of a required color material to be filled. A remaining in the line 7A towards the end of this process Residual amount of the color material can with one from the pig station 6A coming pig into the cylinder 12A are pressed. To Discharge of the line 7A may then be the coating material from the cylinder 12A by advancing the piston the line 27A is first pressed to the atomizer and then with that caused by the automatically controlled piston drive be sprayed exact dosage. For example, can the coating material hereby from the piston dispenser 10A under filling of the entire line 27A promoted in the atomizer become. The required potential separation between the grounded unit 2 and the atomizer will in this case caused by the empty line 7A. Even if the piston dispenser 10A is to be grounded outside the cabin, the potential separation by Isolierstrecken before and behind a limited Color column can be reached between limiting Pig can be conveyed through the pipe 27A, as in the DE 101 31 562 is described. In all cases, the through the pipes pressed on the one hand for the purpose of insulation required draining and cleaning of the line and on the other hand for the promotion of flushing material through the pipe. In the same way, the atomizer 1 of the B-circle be supplied, according to the known A / B technique during spraying a first color from the piston dispenser 10A passed a second color in the piston dispenser 10B and from There can be pressed down to the atomizer.

In a conventional manner, after a coating process in the system remaining material in the metering cylinder and pushed back there into the respective connected ring line and / or returned.

Incidentally, the invention can also be used for systems in which no potential separation is required.

For monitoring and controlling in particular a number of different, Outside the piston dispenser acting factors of the coating system are the piston dispensers 10A and 10B (And possibly the thinner supplying piston dispenser of the mentioned separate rinsing circuit) with a pressure sensor DSA or DSB provided, the continuously prevailing in the cylinder Fluid pressure measures and a pressure corresponding to this e.g. generates electrical signal. For example, the Pressure sensor to the cylinder 12A and 12B with the pig station 28A or 8A or 28B or 8B connecting color channel connected be. But it is also possible, the pressure of the dosing unit 10A and 10B received and funded material if necessary, depending on function or system upstream or downstream to measure the piston dosing. Of a larger number various functions for which the signal of pressure sensors can be used, some are explained below.

A first function of the pressure sensor is the monitoring and regulation of the filling pressure of the piston dispenser. This is important if the dosing cylinder during the return movement of the Piston on the one hand not with negative pressure in relation to the environment, on the other hand, however, with only slight overpressure possible should be filled near zero, e.g. around maximum pressure difference to reach the loop pressure with which the filling is effected. This goal can be achieved, for example, by appropriate Control of the speed of the piston drive to Setting and maintaining a desired pressure setpoint and if necessary shutdown when falling below a pressure limit reached become. The monitoring or regulation of the filling pressure is both when filling from the loop as well as when pushing back of unused material in the dosing cylinder appropriate. Here, the highest possible filling speed be exploited.

An appropriate control possibility also results when the Material the dosing of the piston drive for pressing to the atomizer or to push back the material for example, is taken in a loop, where in each case the pressure with increasing filling of the downstream Hose line and depending on the piston speed (possibly with fluctuations) increases. This is on the one hand the highest possible delivery rate, i. the shortest possible delivery time achieved, but on the other hand, in particular by the strength the hoses or other components specified maximum pressure not be exceeded. To those in the system under Full compliance with the pressure limit to make full use of time savings First, a maximum delivery rate is set or carried out a volume control of the funded material, So volume constant promotion until a predetermined pressure limit is reached. Then, on pressure control with the maximum allowable pressure using the pressure sensor signal switched as actual value.

A similar rule possibility exists also when filling the Dosing cylinder from the loop and when pushing back Unused paint from the atomizer into the dosing cylinder. Again, first to the fastest possible filling set a maximum flow rate or volume control be performed until reaching the pressure sensor a still permissible lower pressure limit (close to zero) is determined, and then to pressure regulation for compliance be switched over the achieved pressure value.

One of the further realizable with the pressure sensor monitoring options is that, for example, during the pressing process with the pressure sensor is determined whether the by friction in particular of the pigs and due to the viscosity of the conveyed material occurring pressure losses in the normal range.

The pressure sensor can also be used when filling the piston dispenser the loop pressure is measured and monitored, i. of the Color printing in the filling of the dosing cylinder over the Color changer 2 each connected loop and its possible fluctuations. The pressure in the metering cylinder corresponds after reaching the piston end position the ring line pressure.

Furthermore, from the measured pressure in the metering cylinder, the viscosity of the respective coating material are determined, as with other system parameters assumed to be known and given the pressure in the metering cylinder according to well known physical laws (inter alia Hagen-Poiseullesches Law) according to the viscosity changes.

The u.a. on the flow rate and viscosity of the pumped material based pressure in the metering cylinder may be particular by compliance of the molded hoses and possibly Also change the piston dispenser undesirable (DE 101 48 097, DE 102 33 633). These pressure changes can also be made by the pressure sensor can be measured, and due to the measurements, e.g. by appropriate control of the piston drive compensation the "hose breathing" or other system softnesses be carried out or supported.

Furthermore, with the pressure sensor, the length or the volume in the system contained hoses and with his For example, signal after installation or replacement compensated for hose length determined by hoses when the measured pressure is in a defined range Way with the hose length changes.

Another way to use the pressure sensor signal is the finding that a newt in operation is one of its end positions reached. When one of the piston dispenser acted upon Newt, for example against a stop in the pig station This is due to a sudden increase in pressure Dosing cylinder noticeable. This can in some cases the otherwise necessary for known reasons external pig sensors saved on magnetic or iron cores of the newts respond and especially in the high voltage range electrostatic Atomizers require considerable effort. With the the pig end position signaling signal of the pressure sensor can expediently further signals, in particular for valve control of the Systems are triggered.

During or outside the normal operation of the dosing system can be used with the pressure sensor critical properties identify or verify the system and its components. An important example of this is the determination of the condition the pigs used, their function in particular is affected by wear. Faulty newts can et al Insufficient cleaning of the pipes and thus not only undesirable contamination of the paint material, but also inadequate electrical insulation during potential separation have as a consequence. When the pressure values at one in operation or for diagnostic purposes carried by a pig the hoses are measured, from predetermined normal values may deviate, this deviation as a measure of the state of wear of the pig in question.

Regardless of his other diagnostic, monitoring or Control functions are used by the pressure sensor DSA, DSB always for overpressure monitoring of the system, e.g. the risk of damage hoses or other components of the system to reliably avoid by impermissibly high pressure. The Pressure sensor signal can be used as a control or warning signal and possibly as Shutdown signal and also for permanent visual pressure indication be used.

If necessary, depending on the application, the Pressure sensor be arranged or formed high voltage resistant so he does not go through in electrostatic coating equipment required high voltage is disturbed and / or his Signals easily led out of the high voltage range can be.

Claims (15)

Method for the metered supply of material to a coating device (1) in a system for the automatically controlled serial coating of workpieces, in which the coating material to be applied by the coating device (1) and / or a rinsing material firstly into a cylinder (12A, 12B) of a dosing unit (10A , 10B) and then supplied to the coating apparatus (1) through a particularly molten conduit (27A, 27B),
wherein in the cylinder (12A, 12B) a piston is moved by a controlled drive for filling or emptying the cylinder (12A, 12B) with a predetermined amount of the coating or rinsing material,
and wherein the coating material is applied in particular with the exact dosage effected by the piston drive,
characterized in that the pressure of the coating or rinsing material present in the cylinder (12A, 12B) of the dosing unit (10A, 10B) or taken to the cylinder is measured by a pressure sensor (DSA, DSB) which is a measurement signal corresponding to the pressure generated,
and that one or more operating parameters of the coating installation are monitored and / or controlled as a function of the measurement signal. A method according to claim 1, characterized in that in response to the measurement signal, the speed of the piston drive of the metering unit (10A, 10B) is controlled or turned off when the cylinder (12A, 12B) is filled and / or if from him material in a supply system pushed back or only to the coating device (1) is pressed. A method according to claim 2, characterized in that the piston drive is regulated in the closed loop for adjusting the pressure according to a desired value. A method according to claim 3, characterized in that for material promotion when pushing out the material from the dosing unit (10A, 10B) and / or when introducing the material into the dosing initially set a maximum flow rate or a control of the delivery volume is performed until a pressure limit is reached and then the pressure control is performed. A method according to claim 1, characterized in that are determined from the measured signal of the pressure and / or pressure fluctuations of the material in the supply system, from which the metering unit (10A, 10B) is filled. A method according to claim 1, characterized in that from the measurement signal, the viscosity of the material is determined, with which the dosing unit (10A, 10B) is filled. A method according to claim 1, characterized in that from the measurement signal caused by pig rubbing in the line (7A, 7B, 27A, 27B) and / or caused by the viscosity of the conveyed material pressure losses are determined. A method according to claim 1, characterized in that from the measurement signal, a control signal for the compensation of pressure changes is obtained, based on changes of system components such as the compliance and / or the length or the volume of a hose line (7A, 7B, 27A, 27B) and / or any other constituent of the dosing system. A method according to claim 1, characterized in that from the measuring signal, a pig signal indicating the pig position is generated when a of the dosing unit (10A, 10B) acted upon pig encounters a stop. A method according to claim 1, characterized in that from the measurement signal of the wear state of a through the pipe (7A, 7B, 27A, 27B) funded pig is determined. Supply system for the metered supply of material to a coating device (1) in a system for the automatically controlled serial coating of workpieces with an in particular piggable line (27A, 27B), through which the coating material and / or a rinsing material can be fed to the coating device (1) applying the coating material,
and a dosing unit (10A, 10B) containing a cylinder (12A, 12B) for receiving the coating or rinsing material to be supplied to the conduit (27A, 27B), in which a piston is driven by a controlled actuator for filling or emptying the cylinder (12). 12A, 12B) is movable with a predetermined amount of material,
wherein the coating material is applied in particular with the exact dosage effected by the piston drive,
characterized in that there is provided a pressure sensor (DSA, DSB) measuring the pressure of the coating and rinsing material located in the cylinder (12A, 12B) of the dosing unit (10A, 10B) or supplied or removed from the cylinder, which pressure sensor measures a pressure signal generated,
and in that a device is provided with which one or more operating parameters of the coating installation are monitored and / or controlled as a function of the measuring signal of the pressure sensor (DSA, DSB). Supply system according to claim 11, characterized in that the piston of the dosing unit (10A, 10B) is driven by a reversible servomotor via a spindle drive or another gear. Dosing unit (10A, 10B) for a system according to claim 11 or 12 with a cylinder (12A, 12B), one of a controlled motor driven or driven piston and a connection for a fluid pressure in the cylinder (12A, 12B) measuring pressure sensor (DSA, DSB). Dosing unit according to claim 13 with at least one attached pigging station (8A, 28A, 8B, 28B). Dosing unit according to claim 13 or 14, the cylinder thereof (12A, 12B) of ceramic or other insulating material formed with a tensile and / or flexural modulus is greater than 10 GPa.

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